Ligand Synergy and Interfacial Dynamics in Multistep Crystallization of Indium Nanocrystals

ABSTRACT Regulating dynamic interfacial phases during nanocrystal nucleation is a key challenge in advancing from classical crystallization to precise functional material synthesis. In this work, we combine in situ liquid‐phase transmission electron microscopy (LP‐TEM) with molecular dynamics (MD) simulations and density functional theory (DFT) calculations to investigate the multistep crystallization and particle fusion processes in an indium halide‐oleylamine system. We identify a dynamic interfacial region that evolves throughout the crystallization pathway. Unlike traditional models, nucleation begins with liquid‐liquid phase separation, forming metastable amorphous intermediates. Nanocrystal growth further involves particle–particle fusion, observed as oriented attachment and coalescence events, with persistent interfacial contrast around the crystalline cores, indicating enhanced interfacial dynamics. By introducing hexadecyl trimethyl ammonium chloride (CTAC) as a tunable halide/surfactant perturbation, we demonstrate that halide‐rich conditions correlate with more dynamic interfacial behavior and increased particle reorientation and reshaping. Aberration‐corrected STEM imaging and EELS analysis provide direct evidence of the structural and chemical evolution of the interfacial region, revealing distinct features at the interface compared to the bulk solution. DFT and MD simulations offer molecular‐level insights into halide‐amine coordination, revealing that chloride ions have stronger adsorption energies than oleylamine molecules, supporting the plausibility of reduced‐indium intermediates. It is hoped that this work establishes a time‐resolved, quantitative framework for understanding multistep crystallization, particle fusion, and interfacial dynamics in a nonpolar, ligand‐rich environment, with significant implications for controlled nanomaterial synthesis.